Air conditioner coils
June 15, 2005 9:11 AM   Subscribe

We had our furnace worked on by a local guy who has a good rep. We mentioned that our air condition had been icing up, and he said we should get the coils cleaned. $300.

The thing is, the compressor unit thingy is outside, it's only a year old, and I can access it with a hose myself. Am I misunderstanding what he's talking about? Should I do this myself? I hear conflicting reports on the internets, stuff like "he hauled out bags and bags of crud." I am lost and confused. Is he talking about cleaning something inside the main furnace unit in the basement? Yes, I will ask him for more info, but wanted to know what your experiences are. Thanks.
posted by mecran01 to Home & Garden (3 answers total)
FWIW, we had our coils cleaned, it was about $300 or so, he found [bags and bags of crud] left by the prior owners of our house. The improvement in the AC was noticeable.

You can clean the outside coil off yourself, have the tech clean just the inside one, that should lower the cost.
posted by neilkod at 9:36 AM on June 15, 2005

We just had our 2-3 year old AC looked at because of ice on coils. There are coils on the outside unit which you can clean yourself with a hose and sprayer. There are also coils in the inside unit. Those would be the ones to form ice. Cleaning those might do some good depending on how old the inside unit is, but you would really want to fix what is causing the ice. In our case the filters (electronic but that does not matter really) were so packed with cat hair, lint, and dirt that there was not enough air flow to the coils. When that happened the coils iced up and the AC barely cooled. Our AC guy told us to keep the filters cleaned and be sure the air intake in the wall was no restricted/blocked. After cleaning the filters and the ice melted it has worked great.
Our AC guy told me that we should see a 15-20 degree drop between the intake and vent temps. Our unit is in a closet with both intake and vent very close to check this.
Not particularly part of every icy coil problem, but we also had trouble with the drip/drain pan's drain pipe on our unit. It was blocked outside which backed up water when the ice melted and tripped the float sensor. The float sensor turns off the outside unit and leaves the inside unit running in "fan mode", no cooling. For a week we had poor cooling with ice forming and melting and turning off the outside unit which was all remedied by cleaning filters and clearing the drain pipe.
When having the unit looked at get the freon levels checked too.
posted by sailormouth at 9:57 AM on June 15, 2005

An evaporator coil in a central A/C is a pretty effective filter. So if the furnace has ever been run with out filters or with poor quality filters what ever wasn't stopped by the filter will get stopped by the coil and block air flow. Blocked air flow creates frost which blocks air flow which creates frost which, well you get the idea. In a short period of time the coil can become completely iced and you have little cooling happening.

Hard to say with out looking whether $300 is reasonable but it isn't out of line, it depends on how much effort is required to access the intake side of the coil. If you can get there thru an access panel a careful brushing with a soft brush (like a natural fiber hair brush) can work wonders on the cheap. Work with the grain of the coil and be careful to not push material farther in and to not touch the fins. For one they are easily bent causing a worse blockage and two they are often very sharp (I've got the scar to prove it :) ). Make sure you turn off power (either at the breaker panel or a switch at the furnace if equiped) to the furance to avoid possible injury and so stuff won't get sucked up if the fan were to come on.

This is also why you should change your filter four times a year. A full filter will block air flow reducing heat/cool output.
posted by Mitheral at 8:22 PM on June 15, 2005

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